Annular combustion chamber with ceramic annular ring

ABSTRACT

An annular combustion chamber for a gas turbine engine in which an annular wall part is made of a ring of ceramic material which is located in the chamber by compression between a frusto-conical first face and a second face which is radial or frusto-conical.

United States Patent [191 Hooke et a].

[ Mar. 19, 1974 ANNULAR COMBUSTION CHAMBER WITH CERAMIC ANNULAR RING [75] Inventors: Noel Harry Hooke, Etwall; Thomas Steel, Littleover; Jack Raymond Bird, Chellaston, all of England [73] Assignee: Rolls-Royce (1971) Limited,

London, England 22 Filed: June 8,1972

211 App]. No.: 261,110

[30] Foreign Application Priority Data June ll, 1971 Great Britain 27471/7] [52] US. Cl. 60/3931, 60/3936 [51] Int. Cl. F020 7/20 [58] Field of Search 60/3931, 39.32, 39.36, 60/200 A [56] References Cited UNITED STATES PATENTS 2,548,485 4/1951 Lubbock 60/200 A 2,924,537 2/1960 Wallis et al. 60/200 A 2,710,523 6/1955 Purvis 60/3932 3,092,962 6/1963 Wood 60/200 A Primary Examiner-Carlton R. Croyle Assistant Examiner-Warren Olsen Attorney, Agent, or Firm-Cushman, Darby & Cushman [57] ABSTRACT An annular combustion chamber for a gas turbine engine in which an annular wall part is made of a ring of ceramic material which is located in the chamber by compression between a frusto-conical first face and a second face which is radial or frusto-conical.

14 Claims, 5 Drawing Figures PATENTEUHAR 19 m SHEET 2 UF 5 mmtsvmwmw 3% mm J A w M mm 1 ANNULAR COMBUSTION CHAMBER WITH CERAMIC ANNULAR RING This invention relates to an annular combustion there has been an increase in the combustion chamber operating temperature over the years which hasrequired the development of new combustion chamber materials which will withstand these higher temperatures. Recently, attention has been focussed on ceramic materials such as silicon nitride. However, since such materials are comparatively brittle and have low coefficients of thermal expansion it has been difficult to provide satisfactory mounting arrangements.

The present invention provides a combustion chamber in which ceramic parts are used and are mounted in an advantageous fashion.

According to the present invention an annular combustion chamber for a gas turbine engine comprises at least part of its annular wall made up of a ring of ceramic material, the ring being located by compression between a complete or interrupted annular frustoconical face and a second complete or interrupted annular face, which may be radial or frusto-conical.

Preferably spring means are provided which urge the faces together; thus this spring means may comprise a corrugated washer which urges the part carrying one said face toward the other said face. In a preferred embodiment the ceramic ring comprises at least the inner portion of the discharge nozzle of the chamber. In this case said annular faces may be located at the same radius and may grip the inner part of the ring, or altematively they may lie on different radii and may grip between the inner and outer peripheries of the ring.

The faces may comprise relieved portions which reduce heat conduction from the ceramic.

A preferred ceramic material comprises hot pressed silicon nitride.

The invention will now be particularly described with reference to the accompanying drawings in which:

' made thin and flexible to allow relative radial move- FIG. 1 is a partly broken away diagrammatic view of a gas turbine engine having a combustion chamber in accordance with the invention,

FIG. 2 is an enlarged section through the combustion In FIG. 2 there is shown an outer casing 16 and a compound inner casing 17 between which lies the combustion chamber proper. This comprises an entry snout 18 through which primary air is fed to the combustion space, and the outer wall 19 and an inner wall 20 which between them define the combustion area. These walls are made up of rings of metal welded together and are provided with holes for wall cooling air and discrete chutes for the ingress of primary and dilution air necessary for combustion. These walls are in accordance with the common Assignees US. Pat. application of Williamson Ser. No. 876,504 filed Nov. 13, 1969. Further discrete chutes provide dilution air which dilutes the hot gases. i

The combustion chamber is also provided with fuel injection means and ignition means which are not visible in the accompanying drawings.

At the downstream end of the chamber the flow area of the chamber is decreased before the gas flows through a row of nozzle guide vanes 21. This reduction is mainly effected by the angular surfaceof the inner part 22 of the discharge nozzle. Since this surface effects a turning of the hot gases, it is one of the hottest areas of the combustion chamber. and therefore in the FIG. 2 embodiment the part 22 is made up of hot pressed silicon nitride.

The part 22 essentially comprises a frusto-conical ring whose inner periphery is formed as a substantially radial flange having a downstream facing radial surface 23 and an upstream facing frusto-conical surface 24. To retain the part 22 in position, the face 24 abuts against a corresponding frusto-conical surface 25 which is carried from part of the inner casing 17. In fact the face 25 is not completely annular but is relieved by radial slots. The relieved face 25 is formed on a ring 26 which is carried by cylindrical extension 27 from a flange 28 bolted to the casing 17. The extension 27 is ment between the hot ring 26 and the cooler flange 28.

To retain the part 22 against the face 25 a ring 29 having its surface 30 relieved as is the face 25 abuts against the face 23 and is urged against it by a corrugated or wave spring washer 31 which in turn bears against a flange 32 by way of an adjusting washer 33 and a static seal ring 34. The flange 32 is bolted to the flange 28 and therefore the corrugated washer 31 urges the ring 29 towards the face 25 and traps the part'22 in position. Since the face 25 is frusto-conical the part 22 is not only located axially but is also given a radial location.

It will be noted that the faces 25 and 30 are relieved, and in this way the area of contact and consequently the heat transfer between the ceramic and metal part is reduced.

Differential expansion and contraction between the various parts is allowed by the resilience of the spring washer. A small radial clearance is arranged between thering 29 and washer 31 and the extension 27, hence allowing them to tilt and allow for small misalignments.

Cooling of the metal parts adjacent to part 22 is provided for. Nozzle guide vane cooling air is divided into twoflows adjacent to the nozzle guide vane support casing 35, a main flow and a small bleed through holes 36 in part 35 to cool heat shield 37 to join main nozzle guide vane flow again. Part 37 forms a static seal with part 34 at its inner periphery and is located at its outer periphery by the nozzle guide vane clamping arrangement.

Flange 26 is cooled by air passing between its upstream surface and flange 38 on part 17. This air passes into the combustion chamber through holes 39 in part 26. Ring 29, wave washer 31 and adjacent parts are cooled by air passing through holes 40 in part 27 through wave washer 31 and thence into the combustion chamber outlet adjacent to the nozzle guide vane inner platform.

In FIG. 3 there is shown an alternative embodiment in which the majority of the chamber is identical to the embodiment of FIG. 2, only the support structure for the part 22 being changed. Consequently only this part of the structure will be described.

Once again the part 22 is provided with the radially extending inner flange on which is formed the face 24, and once again this abuts against the relieved face 25 on the ring 26 which is supported in an identical fashion to the FIG. 2 embodiment. However, in this case the face 23 is not used for location and instead an annular surface 41 is provided on the outer periphery of the part 22. This face bears against a corresponding relieved face 42 formed on an extension piece 43. The extension piece has an inner portion 44 having an annular face similar to that of the part 29 in FIG. 2, and once again a corrugated washer 31 is provided which forces the part 44 and consequently the entire extension piece 43 toward the face 24. Once again the washer 31 is supported from the bolted flange 32 and the spacing washer 33 and static seal 34.

It will be seen that the principle of the FIG. 3 embodiment is similar to that of the FIG. 2 embodiment, but in this case the part 22 is not cantilevered from its inner periphery but is supported over substantially its entire length which is clamped between the faces 41 and 24. Once again similar cooling flows of air to those of FIG. 2 may be provided.

In the FIG. 4 embodiment a greater proportion of the combustion chamber is made up of silicon nitride. The wall 19 and entry snout 18 of the combustion chamber are identical to those of the previous embodiments, but the wall comprises an upstream portion 45 which is made solely of metal parts as before and a downstream section 46 which is made up of an outer wall 47 of metal and an inner wall 61 of silicon nitride. It will be noted that outer and inner in this content mean with respect to the combustion space. The outer wall 47 contains discrete chutes for the entry of primary and dilution air and is located at its downstream end by flange 60 to casing 17. This wall is load bearing and is used to support the inner silicon nitride wall.

The inner wall 46 is made up of a series of cylindrical rings 48, 49 and 50 and an inner discharge nozzle portion 51 which is similar in function to the part 22 of the previous embodiments. The upstream ring 48 has an upstream frusto-conical face 52 which abuts against a corresponding frusto-conical face 53 formed on the metallic outer skin 47. Face 52 may be slotted to minimise heat conduction from ceramic. At its opposite end the ring 48 is provided with a step which forms a reduced diameter portion 54. This portion engages with a corresponding portion 55 of reduced thickness which is similarly formed in the part 49, and a similar arrangement is used to connect the part 49 with the part 50. It will be noted that clearance holes are-provided between the rings for the passage of the air chutes, which direct dilution air into the chamber without allowing it to impinge directly on the ceramic.

To support the ring 50 from the frusto-conical ring 51 the ring 50 has a substantially square downstream end which fits over a step 56 formed in the upstream surface of the inner part of the ring 51. On the opposite face of the inner periphery of the ring 51 a substantially radial surface 57 is formed, and in a similar fashion to the FIG. 2 embodiment a ring 58 with slotted face is caused to press this face by the action of a corrugated spring washer 59. Once again the opposite face of the spring washer is connected to a bolted flange 60, the flange 60 forming part of a bolted up structure which also holds the outer skin 47 in place.

7 It will be seen that in this case the rings 48, 49, 50 and 51 are all retained in place by the spring washer 59 which acts on the ring 58 and clamps the complete assembly against the face 53. Once again the spring washer allows for differential expansion and contraction between the silicon nitride and the adjacent parts.

It will be appreciated that it will be possible to make further parts of the combustion chamber in a similar fashion to those described above. Thus subject to the possibility of manufacturing sufficiently large silicon nitride rings it will be possible to form the wall 19 of the combustion chamber in a similar fashion using a similar method of location. Again, it would be possible to make a greater part of the inner wall of ceramic. It

would also be noted that although the parts described were made of silicon nitride it would be possible to use other ceramic materials if this were desired.

As an alternative to the spigotted location between the rings 48, 49 and 50, their abutting surfaces may be correspondingly frusto-conical as shown at in FIG. 4a, so as to give location. Although in the constructions described above the ceramic portions are trapped between a radial and a frusto-conical face, it would be possible to use two frusto-conical faces for this purpose without losing the advantages of the invention.

We claim:

1. An annular combustion chamber for a gas turbine engine comprising at least one annular wall, an annular ring made of a ceramic material and forming at least a part of the axial length of said wall, support means for supporting said annular ceramic ring, said support means including a first annular frusto-conical face and an axially spaced second annular face opposing said first face and means to urge said first face and said second face towards one another, and said annular ceramic ring having a first frusto-conical face substantially complementary to and abutting said first face of said support means and a second face axially spaced from the first face of said ceramic ring and abutting and substantially complementary to said second face of said support means, said annular ceramic ring being supported under compression in a generally axial direction and being positioned both axially and radially by the urging together of said first face and said second face of said support means. g

2. An annular combustion chamber for a gas turbine engine as claimed in claim 1 in which said second annular face-of said ceramic ring is frusto-conical.

3. An annular combustion chamberfor a gas turbine engine as claimed in claim 1 in which said second annular face of said annular ceramic ring lies substantially in a radial plane of said annular wall part.

4. An annular combustion chamber for a gas turbine engine as claimed in claim 1 in which at least one of the respective abutting faces of said annular ceramic ring and said support means is relieved to reduce contact area between said annular ceramic ring and said support means to thereby reduce heat conduction from the annular ceramic ring.

5. An annular combustion chamber for a gas turbine engine as claimed in claim 1 in which said means to urge said first and second second faces of said support means together is a spring means.

6. An annular combustion chamber for a gas turbine engine as claimed in claim 5 in which said spring means comprises a corrugated spring washer.

7. An annular combustion chamber for a gas turbine 9. An annular combustion chamber for a gas turbine engine as claimed in claim 8 and in which said faces are formed on the first and last members of said plurality of rings whereby said plurality of rings are held together in compression.

10. An annular combustion chamber as claimed in claim 8 and in which the intermediate members of the plurality are retained together by reduced diameter portions which engage with cut-away portions on the next adjacent rings. 7

11. An annular combustion chamber for a gas turbine engine as claimed in claim 1 in which said ceramic material comprises hot pressed silicon nitride.

12. An annular combustion chamber for a gas turbine engine as claimed in claim 7 in which said faces of said support means engage with the respective faces of said annular ceramic ring defining said nozzle inner portion at substantially the same radius.

13. An annular combustion chamber for a gas turbine engine as claimed in claim 7 in which said faces of said support means respectively engage the faces of said annular ceramic ring of said nozzle inner portion at said rings inner and outer peripheries at different radii.

14. An annular combustion chamber for a gas turbine engine as claimed in claim 8 in which the intermediate members of the plurality of rings are retained together by abutting substantially complementary frusto-conical faces. 

1. An annular combustion chamber for a gas turbine engine comprising at least one annular wall, an annular ring made of a ceramic material and forming at least a part of the axial length of said wall, support means for supporting said annular ceramic ring, said support means including a first annular frusto-conical face and an axially spaced second annular face opposing said first face and means to urge said first face and said second face towards one another, and said annular ceramic ring having a first frusto-conical face substantially complementary to and abutting said first face of said support means and a second face axially spaced from the first face of said ceramic ring and abutting and substantially complementary to said second face of said support means, said annular ceramic ring being supported under compression in a generally axial direction and being positioned both axially and radially by the urging together of said first face and said second face of said support means.
 2. An annular combustion chamber for a gas turbine engine as claimed in claim 1 in which said second annular face of said ceramic ring is frusto-conical.
 3. An annular combustion chamber for a gas turbine engine as claimed in claim 1 in which said second annular face of said annular ceramic ring lies substantially in a radial plane of said annular wall part.
 4. An annular combustion chamber for a gas turbine engine as claimed in claim 1 in which at least one of the respective abutting faces of said annular ceramic ring and said support means is relieved to reduce contact area between said annular ceramic ring and said support means to thereby reduce heat conduction from the annular ceramic ring.
 5. An annular combustion chamber for a gas turbine engine as claimed in claim 1 in which said means to urge said first and second second faces of said support means together is a spring means.
 6. An annular combustion chamber for a gas turbine engine as claimed in claim 5 in which said spring means comprises a corrugated spring washer.
 7. An annular combustion chamber for a gas turbine engine as claimed in claim 1 in which said combustion chamber has a discharge nozzle having inner and outer portions, said annular ceramic ring comprising the inner portion of the nozzle.
 8. An annular combustion chamber for a gas turbine engine as claimed in claim 1 and in which there are a plurality of said ceramic rings which abut together to make up said annular wall of the combustion chamber.
 9. An annular combustion chamber for a gas turbine engine as claimed in claim 8 and in which said faces are formed on the first and last members of said plurality of rings whereby said plurality of rings are held together in compression.
 10. An annular combustion chamber as claimed in claim 8 and in which the intermediate members of the plurality are retained together by reduced diameter portions which engage with cut-away portions on the next adjacent rings.
 11. An annular combustion chamber for a gas turbine engine as claimed in claim 1 in which said ceramic material comprises hot pressed silicon nitride.
 12. An annular combustion chamber for a gas turbine engine as claimed in claim 7 in which said faces of said support means engage with the respective faces of said annular ceramic ring defining said nozzle inner portion at substantially the sAme radius.
 13. An annular combustion chamber for a gas turbine engine as claimed in claim 7 in which said faces of said support means respectively engage the faces of said annular ceramic ring of said nozzle inner portion at said rings inner and outer peripheries at different radii.
 14. An annular combustion chamber for a gas turbine engine as claimed in claim 8 in which the intermediate members of the plurality of rings are retained together by abutting substantially complementary frusto-conical faces. 